1. Field of the Invention
The present invention relates to a method for manufacturing a board with built-in electronic elements such as semiconductor elements.
2. Description of the Related Art
In recent years, electronic devices have become more compact and highly functional. Accordingly, demand has increased for a wiring board mounted in an electronic device to be more compact and highly integrated.
In response, various technologies are suggested, such as design to make compact and highly integrated wiring boards by accommodating (building in) electronic elements in a wiring board (for example, technology disclosed in International Publication Number WO 2005/125298.)
The method for manufacturing an electronics module disclosed in International Publication Number WO 2005/125298 is briefly described as follows:
(1) A base material is prepared in which a conductive layer such as copper is disposed on a surface of a support board such as aluminum. On the surface of the board (on the conductive-layer side), multiple concave portions are formed using a laser or the like. Those concave portions are formed so as to correspond to each terminal of an electronic element to be mounted.
(2) By aligning each terminal with its corresponding concave portion, the electronic element is placed on the base material and is secured through an adhesive layer.
(3) On the base material with the placed electronic element, an insulation layer and a conductive layer are laminated and pressed.
(4) Through-holes are formed in the board after pressing, then the conductive layers on both main surfaces of the board are made electrically continuous by copper plating.
(5) Using a subtractive method, a conductive pattern is formed.
In the above manufacturing method, a conductive pattern to be electrically connected to the electronic element is formed by a subtractive method. Here, a subtractive method is a method by which an etching resist is formed on a metal foil or a conductive layer and the portions where the etching resist is not formed are etched away by using an etching solution so that a conductive pattern is formed (see Textbook: Technologies for Printed Wiring Board, published by Nikkan Kogyo Shimbun, Ltd.)
The contents of these publications are incorporated herein by reference in their entirety.